Basically, the RadPane is only the tab which is visualized when you have more than one RadPane placed in a RadPaneGroup. The area where the objects are visible is ContentControl which is not placed in the RadPane. This is the reason the event to be fired only if you have an object defined in the RadPane as the event of the object is send up in the visual tree.
Testing the case in different OS (Windows 7 and Windows 8.1) on our side we receive the same results - the event is not triggered if there are not controls defined in the RadPane.
We would like to have more details about the behavior you're trying to achieve. In most cases hooking to the event of the control defined in the RadPane is helping is to resolve the case.
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